Sedation precludes ~10% of Veterans from colonoscopy due to no escorts. They accept scheduled unsedated colonoscopy. The option effectively manages no shows due to no escort. Other Veterans prefer no sedation. Insertion water exchange (WE) is significantly less painful than air insufflation. The addition of cap-assisted colonoscopy (WECAC) further reduces pain warrants confirmation. Colonoscopists with variable experience will assess generalizability of WECAC vs. WE. Both male and female Veterans will be recruited. Primary Hypothesis: Real-time maximum insertion pain (RTMIP) is significantly lower in the Veterans examined by WECAC vs. WE. Secondary Hypotheses: WECAC produces significantly higher quality colonoscopy outcomes in both male and female Veterans. Exploratory hypotheses: Co-variables affect Veterans' report of RTMIP. Method: Consenting Veterans will be randomized (computer generated random numbers in permuted block design with variable block sizes of 4 and 6), with code revealed at insertion of the endoscope. Gender will be a stratification factor. The investigators will be a blocking factor for the randomization to obtain treatment balance across investigators, however in the analytical phase the data from these investigators will be combined to assess the primary endpoint. Consent covers agreement to be randomized, respond to questionnaires, and allow recording of the examination for analysis, all in a de-identified fashion. State-of-the-art endoscopic equipment is in place. The investigators and support staff have extensive experience in both techniques. To ensure quality performance, both study and control groups are expected to maintain successful cecal intubation rate >95%. Applicable data management, human subject protection, adverse event monitoring and data security measures will be used. Sample size determination. Pilot data by 4 VA investigators in scheduled unsedated male Veterans were updated. The real time maximum insertion pain (RTMIP) [mean (SD)] was 2.7 (2.2) with WE (n=87) and 1.5 (2.1) with WECAC (n=38). The reduction (44%) 2.7-1.5=1.2 is 1.2/2.2=0.55 standard deviation (SD) units. The sample size/group needed to detect a difference at a level of significance of 0.0492 (adjusted for Obrien-Fleming interim stopping rules, one interim analysis at 50% completion) with 90% power is 72 or 144 total using a two-sided two sample t-test. Assuming 90% of subjects will be evaluable, we plan to recruit 160 male Veterans. For the male Veterans, over a 51 month period, 260 will be eligible and approached by research coordinators; 160 (80/arm) will be recruited. After receipt of the critique, the PI identified 9 scheduled unsedated female Veterans (5 WE, 4 WECAC). RTMIP were WE, 6.2 (3.5) and WECAC, 3.5 (3.7). The reduction (44%) was 2.7/3.7 or 0.7 SD unit. The female Veterans had higher RTMIP than the male Veterans, but the percent reduction (both 44%) of RTMIP by WECAC was equivalent. The sample size/group needed to detect a difference at a level of significance of 0.0492 (adjusted for Obrien-Fleming interim stopping rules, one interim analysis at 50% completion) with 90% power is 43 or 86 total using a two- sided two sample t-test. Assuming 90% of subjects will be evaluable, we plan to recruit 96 female Veterans. For the female Veterans, over a 51 month period, 184 to 191 will be eligible and approached by research coordinators; 96 (48/arm) will be recruited. At each VA site, the Women's Health clinic will assist the research coordinator to inform all female Veterans of the availability of the scheduled unsedated option. Data analysis: Prospective data will be analyzed by Fisher exact, ?2, Student t, linear or logistic regression, nonparametric methods and hierarchical model as indicated. Interim analysis will be performed to assess significant efficacy. Significance: Meeting patient unmet needs and preference. Long term goal: To address adenoma detection and interval cancer prevention in unsedated Veterans with the least painful insertion technique.